The present invention relates generally to guiding catheters adapted for insertion into vascular vessels. More particularly, the present invention relates to an improved catheter construction and fabrication method.
Within the medical community, it is well known that a guiding catheter is a tube having a high degree of directional control that is used to place other catheters having little or no directional control into specific areas of the body. In the field of vascular intervention, guiding catheters are particularly useful to guide angioplasty and atherectomy devices deeply into the body cavity such as, inter alia, in the coronary, cerebral and renal areas. Typically each catheter will have a specific tip shape adapted and sized to facilitate insertion into the intended area of use.
The requirements of a good guiding catheter include high torque transmission for engagement, high inner lumen lubricity to facilitate insertion of secondary devices, low kinking characteristics and good tip memory. Additionally it is desirable to provide a smooth distal leading surface to prevent damage to the vascular vessels. It is also desirable to provide a marker near the distal tip of the catheter to enhance its visibility by a fluoroscope.
A wide variety of prior art devices have been developed that address these design requirements. For example, in U.S. Pat. No. 4,425,919, Alston et al. disclose a torque transmitting catheter that includes a longitudinally pre-oriented thin-walled tubular substrate surrounded by a flat wire braid wound over the substrate and held in place by a thin-walled tubular superstate. While the torque transmitting characteristics of such a device are good, I have discovered that the torque transmission, kink resistance and tip memory features of a guiding catheter can be enhanced by splitting the braided layer into two layers and forming the outer member from a material that forms a composite with the braid layers and the inner substrate.
Similarly, U.S. Pat. Nos. 3,485,234 and 4,586,923 issued to Stevens and Gould et al. respectively, describe the construction of curving tip catheters. The walls of the described tubular bodies include an inner tubular member surrounded by a sheath of braided wire. It appears as though the wire sheath is surrounded by a second tubular member. A separate flexible tip portion that does not include a braided layer is provided to facilitate insertion through a branching network of blood vessels. Like the Alston et al. catheter only a single braided layer is disclosed. Further, the second tubular member is not applied as a viscous material that is cured in the final desired shape of the catheter. Rather, it is applied as an extruded tube.
U.S. Pat. No. 3,924,632 issued to Cook also discloses a catheter body for intubation of body organs and vessels. Like the Stevens and Gould et al. devices, Cook discloses a catheter of construction including two tubular members which enclose a braided structure. In this case, the braids are formed of fiberglass bands.
U.S. Pat. No. 2,962,050 issued to Rambero et al. discloses a flexible wire-reinforced hose that includes a pair of braided wire layers. However, the hose disclosed by Rambero et al. is not encased by the flexible housing that both surrounds and impregnates the braided layers for additional strength. Additionally, no attempt is made to form the hose into a curving tip catheter.
The prior art devices have worked adequately for guiding catheters presently being used for angioplasty and the like. However, they typically have an outer diameter no larger than 9 French. This limits their inner diameter to the range of approximately 5.5 French, which works fine for most angioplasty operations. However, as atherectomy methods, such as those disclosed in co-pending U.S. patent application Ser. Nos. 732,691 filed May 10, 1985 and 045,916 filed May 1, 1987 become more popular, larger diameter guiding catheters become desirable and necessary.
In order to facilitate introduction of the guiding catheter into its intended position, it is desirable to provide a tip that can readily be detected by a fluoroscope to allow the doctor to monitor the catheters progress within the vascular system. Typically a gold or platinum band is placed about the distal tip of the catheter to enhance the guiding catheter's visibility within the body. However, such tips are both expensive and relatively difficult to manufacture.